MongoDB查询以替换数组中的值？
使用$set替换数组中的值。首先让我们创建一个包含文档的集合-
> db.replaceValueInArrayDemo.insertOne({"StudentScores":[45,56,78]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd7f0421a844af18acdffb7")
}
> db.replaceValueInArrayDemo.insertOne({"StudentScores":[33,90,67]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd7f0521a844af18acdffb8")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.replaceValueInArrayDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cd7f0421a844af18acdffb7"),
"StudentScores" : [
45,
56,
78
]
}
{
"_id" : ObjectId("5cd7f0521a844af18acdffb8"),
"StudentScores" : [
33,
90,
67
]
}以下是替换数组中的值的查询-
> db.replaceValueInArrayDemo.update({_id: ObjectId("5cd7f0421a844af18acdffb7"), StudentScores:45}, {$set: {'StudentScores.$': 99}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })让我们再次检查文档-
> db.replaceValueInArrayDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cd7f0421a844af18acdffb7"),
"StudentScores" : [
99,
56,
78
]
}
{
"_id" : ObjectId("5cd7f0521a844af18acdffb8"),
"StudentScores" : [
33,
90,
67
]
}